两道关于算法的面试题

 1 package test1;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 public class TestStack {
 7 
 8     private List<Character> elements = new ArrayList<>();
 9 
10     private void in(Character o) {
11         this.elements.add(o);
12     }
13 
14     private Character out() {
15         int length = this.elements.size();
16         if (length > 0) {
17             return elements.remove(length - 1);
18         }
19         return null;
20     }
21 
22     public int size() {
23         return this.elements.size();
24     }
25 
26     public boolean valid(String str) {
27         this.elements.clear();
28         if (str != null && str.length() > 0) {
29             char[] chars = str.toCharArray();
30             for (char c : chars) {
31                 char left1 = '(';
32                 if (c == left1) {
33                     this.in(c);
34                 }
35                 char right1 = '[';
36                 if (c == right1) {
37                     this.in(c);
38                 }
39                 char left2 = ')';
40                 if (c == left2) {
41                     char outElement = this.out();
42                     boolean r = outElement == left1;
43                     if (!r) {
44                         return false;
45                     }
46                 }
47                 char right2 = ']';
48                 if (c == right2) {
49                     char outElement = this.out();
50                     boolean r = outElement == right1;
51                     if (!r) {
52                         return false;
53                     }
54                 }
55             }
56         }
57         return this.elements.size() == 0;
58     }
59 }

 1 package test1;
 2 
 3 public class TestDemo {
 4     public static void main(String[] args) {
 5         String str1 = "()";
 6         String str2 = "[]";
 7         String str3 = "(]";
 8         String str4 = "((()";
 9         String str5 = "()[()]";
10         String str6 = "([)]";
11         String str7 = "()[()()]([][])[()[[[[]]]]]";
12 
13         TestStack testStack = new TestStack();
14         System.out.println(str1 + ": " + testStack.valid(str1));
15         System.out.println(str2 + ": " + testStack.valid(str2));
16         System.out.println(str3 + ": " + testStack.valid(str3));
17         System.out.println(str4 + ": " + testStack.valid(str4));
18         System.out.println(str5 + ": " + testStack.valid(str5));
19         System.out.println(str6 + ": " + testStack.valid(str6));
20         System.out.println(str7 + ": " + testStack.valid(str7));
21     }
22 }

 1 package test2;
 2 
 3 import java.util.Arrays;
 4 
 5 public class TestDemo {
 6     public static void main(String[] args) {
 7         int[] arr1 = {1, 3, 5, 9, 15};
 8         int[] arr2 = {2, 5, 7, 8, 12, 13, 19};
 9 //        int[] arr1 = {1, 2, 3, 4};
10 //        int[] arr2 = {1, 2, 3};
11 //        int[] arr1 = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1};
12 //        int[] arr2 = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
13 
14         int[] newArr = new int[arr1.length + arr2.length];
15         int point1 = 0;
16         int point2 = 0;
17 
18         for (int i = 0; i < newArr.length; i++) {
19             if (point1 >= arr1.length && point2 < arr2.length) {
20                 newArr[i] = arr2[point2++];
21                 continue;
22             }
23             if (point1 < arr1.length && point2 >= arr2.length) {
24                 newArr[i] = arr1[point1++];
25                 continue;
26             }
27             int result = Integer.compare(arr1[point1], arr2[point2]);
28             switch (result) {
29                 case -1:
30                     newArr[i] = arr1[point1];
31                     point1++;
32                     break;
33                 case 0:
34                     newArr[i++] = arr1[point1];
35                     newArr[i] = arr2[point2];
36                     point1++;
37                     point2++;
38                     break;
39                 case 1:
40                     newArr[i] = arr2[point2];
41                     point2++;
42                     break;
43             }
44         }
45         System.out.println(Arrays.toString(newArr));
46     }
47 }